Staggered Cell Arrangement Improves EV Battery Pack Thermal Performance

Thermal management remains a fundamental challenge in electric vehicle battery development, directly influencing cell lifespan, safety margins, and overall system reliability. This computational study investigates how the physical arrangement of cylindrical lithium-ion cells within a battery pack affects heat dissipation under passive cooling conditions. Researchers developed a reduced-order thermal model of a 13-cell, 8-parallel (13S8P) battery pack using commercial 18650-format cells and compared two competing geometries: staggered (zig-zag) and inline (aligned) cell arrangements. The analysis spanned eight discharge rates from low auxiliary-load scenarios to peak acceleration demands, incorporating realistic temperature-dependent cell resistance and industry-standard natural convection correlations. Results demonstrate that the staggered arrangement consistently outperforms the inline configuration, achieving a mean maximum-temperature reduction of 1.3°C—equivalent to 14.5% of the total temperature rise above ambient conditions. This benefit scales with discharge rate, reaching 2.0°C reduction at peak current levels. The staggered arrangement enhances the mean convective heat transfer coefficient by approximately 71%, directly attributable to improved airflow distribution around cells. Both configurations maintain safe operating temperatures below 45°C up to 40 amperes of discharge current. At 50 amperes, temperatures approach this thermal limit, but the staggered arrangement provides an additional 1.9°C safety margin—potentially extending battery cycle life and reducing thermal management system complexity. Importantly, this performance gain requires no active cooling, weight penalty, or manufacturing cost increase; it results purely from geometric optimization of cell positioning. The study's reduced-order model demonstrates convergence through rigorous time-step refinement analysis. While the authors acknowledge that computational methods cannot fully resolve internal airflow patterns and suggest experimental or computational fluid dynamics validation for detailed uniformity analysis, the findings provide actionable design guidance for battery engineers. The work establishes that simple geometric modifications can substantially enhance thermal performance in passive cooling scenarios, offering original equipment manufacturers a straightforward optimization lever for improving battery durability and safety margins in electric vehicle applications.